Five lines on his chart represent the Electric Power, Transportation, Industrial, Residential, Commercial sectors. The X axis lists the years 1990 through 2003. The Y axis represents the percentage of Total metric Tons of CO2. Electric Power accounts for the larges percentage of CO2 emissions, from between about 36-38%. For electric Power, there was a slight increase in the percentage of CO2 emissions around 1997. The Transportation sector makes up the next highest percentage of CO2, between 31-33% of the total. This percentage has remained fairly stable between 1990 and 2003, with only a very slight percentage increase around 1998. The Industrial sector began at about 22% and dropped below 20% in 1998 and down to 18% in 2003. The Residential sector has remained at about 7% of CO2 emissions and the Commercial sector has been steadily around 4-5%.